Fan wheel of an axial ventilator

ABSTRACT

An axial ventilator has multiple fan wheel blades ( 2 ) arranged around an axis of rotation (RA) in a blade ring. At least one of the fan wheel blades ( 2 ) has an inner section ( 3 ) located on the radial inside. A blade edge section ( 4 ) directly adjoins the inner section ( 3 ) and borders a blade edge ( 5 ). The at least one fan wheel blade ( 2 ) has a local projection ( 6 ) over a radial extension of the blade edge section ( 4 ). The local projection ( 6 ) is formed as an extension of the chord length of the fan wheel blade. The projection locally enlarges the fan wheel blade ( 2 ) in the blade edge section ( 4 ). An average angle of attack (α) of the fan wheel blade ( 2 ), in relation to a plane of rotation (RE), of the fan wheel ( 1 ), is larger than an average angle of attack (β) of the projection ( 6 ), in relation to the plane of rotation (RE).

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Application No. 10 2019 105355.2, filed Mar. 4, 2019. The disclosure of the above application isincorporated herein by reference.

FIELD

The disclosure relates to an axial ventilator fan wheel, with multiplefan wheel blades arranged around an axis of rotation in a blade ring.

BACKGROUND

Generic axial ventilators fan wheels that generate an axial airflow havebeen known for some time. Typically, they include a plurality of fanwheel blades. The blades, extending radially outward and originatingfrom the hub, are arranged in a blade ring.

The noise generated due to turbulence is problematic. In particular, ininstallation conditions that are impaired with respect to the incomingflow and/or incident flow.

The disclosure is based on an object of providing a fan wheel thatensures a reduction of the noise level generated in operation, inparticular, in such impaired installation conditions.

SUMMARY

This object is achieved by the feature combination according to an axialventilator fan wheel with multiple fan wheel blades arranged around anaxis of rotation (RA) in a blade ring. At least one of the fan wheelblades includes an inner section located on the radial inside and ablade edge section directly adjoining the inner section and bordering ablade edge. The at least one fan wheel blade comprises a localprojection over a radial extension of the blade edge section. Theprojection is formed as an extension of a chord length of the fan wheelblade and locally enlarges the fan wheel blade in the blade edgesection. An average angle of attack (α) of the fan wheel blade, inrelation to a plane of rotation of the fan wheel, is larger than anaverage angle of attack (β) of the projection, in relation to the planeof rotation (RE).

According to the disclosure, an axial ventilator fan wheel is proposedwith multiple fan wheel blades arranged around an axis of rotation in ablade ring. At least one of the fan wheel blades comprises an innersection located on the radial inside and a blade edge section directlyadjoining the inner section and bordering a blade edge. The at least onefan wheel blade comprises a local projection over a radial extension ofthe blade edge section. The projection is formed as an extension of thechord length of the fan wheel blade. This locally enlarges the fan wheelblade in the blade edge section. The blade edge section is thusdelimited from the inner section and defined in that the projection isalways provided. Furthermore, it is essential to the disclosure that anaverage angle of attack of the fan wheel blade, in particular in theblade edge section, in relation to a plane of rotation of the fan wheelis greater than an average angle of attack of the projection in relationto the plane of rotation.

The combination of the technical features, (1) the projection with anenlarged chord length in the blade edge section and (2) reducing theangle of attack of the projection in relation to the axis of rotation inrelation to the remaining fan wheel blade at the same time, decreasesthe tendency of the flow to break away at the fan wheel and thereforedecreases the blade passing noise, which is perceived to be particularlyunpleasant.

In the fan wheel, one preferred embodiment has the average angle ofattack of the projection, in relation to the plane of rotation of thefan wheel, at an angle between 1-15°, more preferably between 3-10°. Theangle of attack of the projection is always less in this case than thatof the fan wheel blade in the region outside the projection.

Many axial ventilator fan wheels use a ring clamped around the fan wheelblades on the radial exterior. This is frequently referred to as aslinging ring. One advantageous embodiment of the fan wheel of thepresent disclosure is especially directed to the fan wheel blades endingfreely. The blades are free of connection at the respective radial bladeedges. Thus, no ring or the like connects the fan wheel blades at theradial exterior. The radial outside blade edges of the fan wheel bladesare fluidically uninfluenced by the free end. Thus, the effect of theprojection is favorably applied.

Furthermore, preferably the fan wheel blade edge section of the at leastone fan wheel blade adjoining the blade edge is defined in a radialouter region of the fan wheel blade. The size of this radial outerregion and thus the radial extension of the projection is defined by theratio of the radius LS of the fan wheel blade up to the blade edgesection to the maximum radius of the fan wheel blade LD. Accordingly0.7≤LS/LD≤1, preferably 0.85≤LS/LD≤0.95 applies.

With respect to the extension of the projection in the circumferentialdirection in the plane of rotation of the fan wheel, preferably thechord length of the fan wheel blade is locally enlarged by the extensionin a direction perpendicular to the axis of rotation. This occurs inrelation to the inner section such that 1.05≤L1/L2≤1.4, more preferably1.1≤L1/L2≤1.3 applies. L1 is the maximum chord length of the blade edgesection. L2 is the chord length of the fan wheel blade at the borderbetween the intersection and the blade edge section. Each are measuredat the blade edge located on the radial outside of the fan wheel blade.

The fan wheel blades each comprise a blade front edge and a blade rearedge. One particularly advantageous effect for noise reduction isachieved if the projection is formed on the blade front edge. The bladerear edge in turn has a complex curved, arc-shaped profile in onefavorable embodiment. The blade front edge is preferably also a curvedarc shape, but has a larger radius, in particular, multiple times largerthan that of the blade rear edge.

Moreover, an embodiment variant of the fan wheel is advantageous wherethe projection is formed in one piece with the fan wheel blade. The fanwheel is preferably manufactured from plastic. Thus, all technicalfeatures influencing the flow are integrally formed in the fan wheelblades.

In one refinement of the fan wheel, the projection comprises a tippointing in the circumferential direction. The tip is preferably spacedapart radially inward in relation to a maximum outer radius of the fanwheel blade. This means that the projection is indented radially inward.The tip preferably defines an imaginary circle in operation. The circleis spaced apart in relation to the outer radius of the fan wheel.

Furthermore, an embodiment variant of the fan wheel is advantageouswhere the tip of the projection is offset radially outward off-center inthe blade edge section. In other words, the projection is formed in sucha way that its tip pointing in the circumferential direction is locatedcloser to the outer radius than to the inner section of the fan wheelblade.

Furthermore, a design of the fan wheel blades includes the tip of theprojection rounded in each case. This has a fluidically advantageous andnoise-reducing effect in the fan wheel.

In further advantageous embodiments of the fan wheel, the fan wheelblades each comprise a winglet at the radial outer blade edge. A wingletis defined as a formation on the fan wheel blade. It has a thickening orrounding from the lower side to the upper side at the radial end on thefan wheel blade. Moreover, brushes can optionally be provided in eachcase at the radial outer blade edge.

In a further embodiment, the fan wheel blades have a lesser averageblade thickness at least along the projection than in the remainingregion of the respective fan wheel blades.

The fan wheel blades each define a radial center region around theradial center. Here, the chord length of the fan wheel blade has amaximum. The center region preferably extends in this case up to 30% ofthe radial maximum extension of the fan wheel blades around the radialcenter.

Furthermore, in a preferred embodiment of the fan wheel, the fan wheelblades are formed identically.

The disclosure furthermore comprises an axial ventilator with theabove-described fan wheel.

DRAWINGS

Other advantageous refinements of the disclosure are found in thedependent claims and/or are described in greater detail hereaftertogether with the description of the preferred embodiment of thedisclosure on the basis of the figures. In the figures:

FIG. 1 is an axial top plan view of a fan wheel according to thedisclosure.

FIG. 2 is a side elevation view of the fan wheel according to FIG. 1.

FIG. 3 is an enlarged perspective detail view of a fan wheel blade ofthe fan wheel according to FIG. 1 from the axially opposing side,

FIG. 4 is an enlarged elevation profile view of the radial blade edge ofthe fan wheel blade of the fan wheel from FIG. 1.

FIG. 5 is an enlarged elevation profile view on the radial blade edge ofa fan wheel blade fan wheel from FIG. 1.

FIG. 6 is a diagram of the sound pressure level in relation to thefrequency in the case of the fan wheel from FIG. 1 in relation to a fanwheel of the prior art.

FIG. 7 is a diagram of the angle of attack of the fan wheel blades fromFIG. 1 in relation to the prior art.

FIG. 8 is a diagram of the chord length of the fan wheel blade from FIG.1 in relation to the prior art.

DETAILED DESCRIPTION

FIGS. 1-5 shows an exemplary embodiment of a fan wheel 1 of an axialventilator. Five identical fan wheel blades 2 originating from the hub17 extend radially outward from it. A blade ring is formed around theaxis of rotation RA. The number of the fan wheel blades 2 is establishedas five solely by way of example. However, the number can also be higheror lower in alternative embodiments.

Each fan wheel blade 2 has a blade rear edge 8, a blade front edge 9,and a free ending radial blade edge 5. The individual fan wheel blade 2are exclusively connected via the hub 17. The blade rear edges 8 areconvexly rounded protruding in the circumferential direction and eachdefines an arc-shaped profile. The blade front edges 9 extend radiallyoutward essentially linearly originating from the hub 17. As can be seenwell in FIG. 2, the fan wheel blades 2 are formed bulging and inclinedin relation to the plane of rotation RE. Reinforcing ribs 25, aligned inthe circumferential direction, are formed on the respective axial lowerside. The ribs extend partially up to the hub 17 and are connected overa predetermined axial extension.

The fan wheel blades 2 each comprise an inner section 3 located on theradial inside and a blade edge section 4. The blade edge section 4 isdirectly on the inner section 3 viewed in the radial direction andextends up to the respective blade edge 5. A dashed line is shown inFIG. 1 as the border 13 between the inner section 3 and the blade edgesection 4. The blade edge section 4, located on the radial outside, isdefined in each of the fan wheel blades 2. It includes the localprojection 6 over its radial extension.

The projection 6 enlarges the chord length of the respective fan wheelblade 2 locally in the circumferential direction in the blade edgesection 4. The border 13 is thus established at the point where theprojection 6 begins. The projection 6 is formed in the embodiment shownat the respective blade front edge 9 in an essentially triangular basicshape. The projection 6 includes a rounded tip 10 pointing in thecircumferential direction. A line is identified by the reference sign 12in FIG. 3. The line indicates the position of the tip 10 in parallel tothe blade edge 5. In this case, it is recognizable that the tip 10 ofthe projection 6 is spaced apart radially inward in relation to amaximum outer radius of the fan wheel blade 2. Thus, the tip 10 isoffset radially outward off-center viewed in the radial direction in theblade edge section 4. This is achieved by different angle profiles ofthe outer edges of the projection 6, that are formed, on the one hand,by the blade front edge 9, on the other hand, by the blade edge 5.

With reference to FIG. 4, the different average angles of attack α, β ofthe fan wheel blades 2 are shown in comparison to the projection 6. Eachangle is in relation to the plane of rotation RE. The average angle ofattack α of the fan wheel blades 2 in relation to the plane of rotationRE is 35°. The average angle of attack β of the projection 6 in relationto the plane of rotation RE corresponds to 10°. Moreover, each angle ofattack along the fan wheel blades 2, in relation to the plane ofrotation RE, is always larger than each angle of attack along theprojection 6, in relation to the plane of rotation RE. Furthermore, inFIG. 5, the total angle of attack μ of the fan wheel blades 2 along thechord length L is shown in the center region MB around the radialcenter. Chord length L connects the edge point XV1 at the blade rearedge 8 to the edge point XV2 at the blade front edge 9. In the centerregion MB, the chord length L has its maximum.

In the embodiment shown, the projection 6 is formed in one piece on thefan wheel blade 2, similarly its extension and the chord lengtheningthus caused can be uniquely defined and delimited via the sudden profilechange of the blade front edge 9. Alternative embodiments provide thatthe extension is fastened as an add-on part on the respective fan wheelblade.

The projection 6 in the blade edge section 4 occupies a radial extensionthat is defined via the ratio LS/LD, which is 0.88 in the case shown. LSis the radius of the fan wheel blade 2 up to blade edge section 4. LD isthe maximum outer radius of the fan wheel blade 2. The radius LS/LD isto be between 0.7-1, in particular, between 0.85-0.98.

The size of the projection 6 in the circumferential direction isestablished via the different chord length. The chord length of the fanwheel blade 2 is enlarged by the projection 6 in the directionperpendicular to the axis of rotation RA in such a way that the ratio ofthe maximum chord length L1 of the fan wheel blade 2, including theprojection 6, in relation to the chord length L2 of the fan wheel blade2, without the projection 6, is 1.2. The ratio is to be defined as1.05-1.3, in particular, between 1.1-1.2. Furthermore, the bladethickness of the projection 6 can optionally be greater than the bladethickness of the remaining fan wheel 2, as shown in FIG. 4.

FIG. 6 shows the advantages achieved by the design according to thedisclosure of the fan wheel 2 for reducing the sound pressure level Lpat the different frequencies f. The solid line 77 represents the resultof the fan wheel 2 according to FIG. 1. The dashed line 88 indicates anidentical fan wheel without projection 6. The sound pressure level canbe significantly reduced essentially over the entire frequency curve,but in particular at very low frequencies.

FIG. 7 shows a comparison of the ratio of the angle of attack μ to themaximum angle of attack μ_max of the fan wheel blade 2 having theprojection 6 from FIG. 1 over the radial curve of the radius r to themaximum radius r_max in relation to the prior art (dashed line) withouta projection. The falling angle of attack at the beginning of the bladeedge section 4 can be seen well at a ratio r/r_max of 0.9.

FIG. 8 shows a diagram of the chord length L in relation to the maximumchord length L_max of the fan wheel blade 2 having the projection 6 fromFIG. 1 over the radial curve of the radius r in relation to the maximumradius r_max in relation to the prior art (dashed line) without aprojection. The maximum of the chord length is 0.7 of the total radialextension of the fan wheel blade 2. The chord length is enlarged locallyby the projection 6 in the blade edge section 4.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. An axial ventilator fan wheel with multiple fanwheel blades arranged around an axis of rotation in a blade ringcomprising a fan hub with at least one fan blade radiating from the hub,the at least one of the fan wheel blades comprises: an inner sectionextending from the hub and located on the radial inside and a blade edgesection directly adjoining the inner section and bordering a blade edge;the at least one fan wheel blade comprises a local projection over aradial extension of the blade edge section, the projection is formed inextension of a chord length of the fan wheel blade and locally enlargesthe fan wheel blade in the blade edge section; and an average angle ofattack (α) of the fan wheel blade, in relation to a plane of rotation ofthe fan wheel, is larger than an average angle of attack (β) of theprojection, in relation to the plane of rotation (RE).
 2. The fan wheelaccording to claim 1, wherein the angle of attack (β) of the projection,in relation to the plane of rotation, has a value between 2-15°, inparticular, between 4-10°.
 3. The fan wheel according to claim 1,wherein the fan wheel blades end freely and are free of connections atthe respective radial blade edges.
 4. The fan wheel according to claim1, wherein the blade edge section, adjoining the blade edge, of the atleast one fan wheel blade is defined in an outer region of the fan wheelblade, such that 0.7≤LS/LD≤1, in particular 0.85≤LS/LD≤0.95 applies, andLD is a maximum radius of the fan wheel blade and LS is a radius of thefan wheel blade up to the blade edge section.
 5. The fan wheel accordingto claim 1, wherein a chord length of the fan wheel blade is locallyenlarged in relation to the inner section by the projection in adirection perpendicular to the axis of rotation, such that1.05≤L1/L2≤1.4, in particular 1.1≤L1/L2≤1.3 applies, and L1 is a maximumchord length of the fan wheel blade in the blade edge section and L2 isa chord length of the fan wheel blade at the border between the innersection and the blade edge section.
 6. The fan wheel according to claim1, wherein the at least one fan wheel blade comprises a blade front edgeand a blade rear edge, and the projection is formed on the blade frontedge.
 7. The fan wheel according to claim 6, wherein the blade rear edgehas a convexly rounded, arc-shaped profile.
 8. The fan wheel accordingto claim 1, wherein the projection is formed in one piece with the fanwheel blade.
 9. The fan wheel according to claim 1, wherein theprojection comprises a tip pointing in the circumferential direction,the tip is spaced apart radially inward in relation to a maximum outerradius of the fan wheel blade.
 10. The fan wheel according to claim 9,wherein the tip is offset radially outward off-center in the blade edgesection.
 11. The fan wheel according to claim 9, wherein the tip isrounded.
 12. The fan wheel according to claim 1, wherein the fan wheelblades each comprise a winglet on the radial outer blade edge.
 13. Thefan wheel according to claim 6, wherein the fan wheel blades have agreater average blade thickness in the region of the projection than inthe remaining region of the fan wheel blade.
 14. The fan wheel accordingto claim 1, wherein the fan wheel blade comprise a radial center sectionaround a radial center of the respective fan wheel blade and the fanwheel blade has a maximum chord length in the center region.
 15. The fanwheel according to claim 1, wherein all fan wheel blades of the fanwheel are formed identically.
 16. An axial ventilator comprising a fanwheel according to claim 1.